U.S. Pat. No. 6,281,514, U.S. Pat. No. 6,117,344, U.S. Pat. No. 6,531,703 and U.S. Pat. No. 6,495,843 disclose a method for promoting the passage of elementary particles at or through a potential barrier comprising providing a potential barrier having a geometrical shape for causing de Broglie interference between said elementary particles is disclosed. Also disclosed is an elementary particle-emitting surface having a series of indents. The depth of the indents is chosen so that the probability wave of the elementary particle reflected from the bottom of the indent interferes destructively with the probability wave of the elementary particle reflected from the surface. This results in the increase of tunnelling through the potential barrier. When the elementary particle is an electron, and potential barrier is surface of the substance electrons tunnel through the potential barrier, thereby leading to a reduction in the effective work function of the surface.
WO03083177 discloses modification of a metal surface with patterned indents that increases the Fermi energy level inside the metal, leading to a decrease in electron work function. Also disclosed is a method for making nanostructured surfaces having perpendicular features with sharp edges.